Pivotably-mounted master cylinder and pedal lever arrangement

ABSTRACT

An actuating arrangement for a compact master cylinder includes a foot pedal pivotably connected to support bracket. The cylinder is pivotably connected at its lower end to the foot pedal and at its upper end to the bracket so that movement of the pedal causes movement of the piston into the cylinder and also moves the entire cylinder in relation to the supporting structure.

This is a Divisional of application Ser. No. 177,418 filed Apr. 4, 1988,now U.S. Pat. No. 4,910,962 dated Mar. 27, 1990.

BACKGROUND OF THE INVENTION

This invention relates to actuators for fluid pressure systems. Anexample system to which the invention is applicable is a hydraulicallyoperated vehicle clutch system, but the invention has other applicationsincluding hydraulic brake systems.

Hydraulic clutch systems typically include a master cylinder which isoperated to generate the primary driving force and therefore functionsas the system actuator, and a slave cylinder which responds to thatforce so as to cause operation of the clutch. A foot pedal is generallyused as the device through which operation of the master cylinder isachieved. A reservoir containing a supply of hydraulic fluid isconnected into the system, usually to the master cylinder, so as to makeup for fluid losses which may occur over a period of time.

It is usual to mount the foot pedal and the master cylinder onrespective opposite sides of the vehicle fire wall, and the mastercylinder needs to be firmly mounted so that the forces generated(primarily tensile) during operation are fully reacted. That is, anydeflection of the master cylinder or its mounting will disturb theeffectiveness of the system. Such a rigid mounting of the mastercylinder presents difficulties and adds to manufacturing andinstallation costs.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a simple and yeteffective actuator for a fluid pressure system. In one particular form,it is an object of the invention to provide an improved master cylinderfor use in a hydraulic fluid system, such as a clutch or brake system.It is another object of the invention to provide an improved actuatorassembly.

According to the invention, there is provided an actuator for a fluidpressure system, including:

a body having a cylindrical bore therein,

a piston having a head portion slidably mounted in said bore and a stemwhich projects out of said body through one end thereof,

a pressure chamber having one part formed within said body between saidhead portion and an end wall of said body at the end thereof remote fromsaid one end, a passage within said piston forming another part of saidpressure chamber and being in communication with the first said part ofthe pressure chamber,

a fluid reservoir,

orifice means connecting the interior of said fluid reservoir with saidpassage,

valve means operable to close said orifice means in response to movementof said piston towards said end wall, and

a fluid outlet connected to said chamber.

The actuator may be utilized with a foot pedal to provide a pedalactuator suitable for use as a brake or clutch pedal or likeapplications.

An actuator and pedal actuator having features as aforesaid can beconstructed in various ways but it will be convenient to hereinafterdescribe a particular embodiment of each.

The embodiments of the invention described in detail in the followingpassages of the specification make reference to the accompanyingdrawings. The drawings are, however, merely illustrative of how theinvention might be put into effect so that the specific form andarrangement of the various features as shown is not to be understood aslimiting on the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross-sectional side view of one embodiment of actuatoraccording to the invention,

FIG. 2 shows an enlarged cross-sectional side view of a part of theactuator of FIG. 1,

FIG. 3 shows a part cross-sectional side view of a pedal assemblyincluding the actuator of FIG. 1, and

FIG. 4 shows a part cross-sectional front view of the assembly of FIG.3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

It will be convenient to hereinafter describe the invention as appliedto a vehicle hydraulic clutch system, but as previously explained thatis not the only application of the invention.

The form of actuator 1 shown in FIG. 1 comprises a master cylinder 2which is composed wholly or substantially of plastics material.Different plastics materials may be selected for different components ofthe actuator according to the respective use conditions of thosecomponents.

The body of the actuator shown is in the form of a tubular member orcylinder 3 which is open at one end 4 and closed at the other end 5 byan end wall 6. A mounting flange 7 projects outwardly from that end wall6 for a reason hereinafter made clear. The interior of the cylinder 3 isdefined by a cylindrical bore 8 which is preferably of constant diameterover at least a substantial part of its length.

A piston 9 is slidably mounted in the cylinder bore 8 and is connectedto a stem 10 which projects axially out of the cylinder 3 through theopen end thereof. Preferably, the piston 9 and the stem 10 areintegrally formed from a suitable plastics material. Sealing means maybe provided on the piston 9 for sliding engagement with the surroundingbore surface 8. In the embodiment shown this sealing means comprises apair of O-ring seals 11. Any suitable stop means 12 may be provided ator adjacent the open end 4 of the cylinder 3 to restrain the piston 9against movement through that open end 4. In that regard, the stem 10has a diameter less than that of the piston 9.

Biasing means such as a coil compression spring 13 acts between thepiston 9 and the body end wall 6 so as to normally urge the piston 9towards a rest position at which it is adjacent the body open end 4engages the stop means 12 secured to the cylinder 3. The part of thecylinder bore 8 between the piston 9 and the body end wall 6 formsportion of a pressure chamber 14. In the arrangement shown, anotherportion of that chamber 14 is formed by an axial bore 15 formed in thepiston 9 and extending into the associated stem 10. That bore 15 extendsthrough the piston end 16 adjacent the cylinder end wall 16. Thepressure chamber 14 is connected to an outlet line 16 through an outletport 17 provided through a side wall 18 of the piston stem 10,preferably at a location remote from the end of the stem 10 which isconnected to the piston 9.

A fluid supply reservoir 19 is connected to the hollow stem 10 ratherthan direct to the cylinder body 3 as in prior actuators. That reservoir19 includes a hollow body 20 which may be formed integral with the endof the stem 10 which is remote from the piston 9. A transverse wall 21separates the interior of the reservoir 19 from the stem bore 15 and anorifice 22 is provided through that wall 21 to permit transfer of fluidbetween the reservoir 19 and the pressure chamber 14. Fluid may beintroduced into the reservoir 19 through an access opening positionedremote from the piston stem 10, and removable closure 24 is providedover that opening.

Valve means 25, clearly shown in FIG. 2, is associated with theaforementioned orifice 22 and is operable to close that orifice 22 whenthe actuator 1 is being operated to cause the piston 9 to move towardsthe end wall 6 of the cylinder body 3. It is preferred that the valvemeans 25 is retained in an orifice open position when the piston 9 is atits rest position so that fluid can pass from the reservoir 19 to thepressure chamber 14 in order to make up for any losses occurring duringoperation of the actuator 1.

In the form shown, the valve means 25 includes a closure element 26which is located within the piston stem bore 15 and includes a headportion 27 arranged to engage an annular valve seat 28 extending aroundthe aforementioned orifice 22. That valve seat 28 is depicted having afrusto-conical form, but that is not essential. The head portion 27preferably includes a part-spherical section 29 which forms a terminalextremity of the closure element 26 and which is connected to a circularflange 30 or boss through a neck 31 of reduced diameter. It is preferredthat a flexible cap 32 of rubber or other suitable elastomeric materialis snap-engaged over that part-spherical section 29 so as to form thevalve seat engaging surface of the closure element 26.

Any suitable retaining means 33 may be provided to retain the closureelement 26 in an orifice open position when the piston 9 is at its restposition. In the construction shown, that retaining means 33 includes atubular member 34 which is held against or secured to the end wall 6 ofthe cylinder body 3, and a rod 35 which connects the aforementioned headportion 27 to that tubular member 34. The rod 35 may be formed integralwith the head portion 27 and extends axially from that head portion 27towards the cylinder body end wall 6. The tubular member 34 extendsaxially from that end wall 6 towards the cylinder open end 4 and in thearrangement shown projects into the piston bore 15 with clearance.

The connection between the rod 35 and the tubular member 34 is such asto permit limited relative axial movement between those components. Inthe depicted arrangement, the rod 35 extends through an opening 36 inthe adjacent end of the tubular member 34 and is slidable within thatopening 36 to permit relative axial movement between the rod 35 andtubular member 34. The end portion of the rod 35 located within thetubular member 34 is provided with an enlargement 37 which is engageablewith a transverse abutment surface 38 of the tubular member 34. Theenlargement 37 and abutment surface 38 engage when the piston 9 is inits rest position and thereby hold the head portion 27 clear of thevalve seat 28 so that fluid can pass between the reservoir 19 and thepressure chamber 14.

When the actuator 1 is operated, the piston 9 moves further into thecylinder body 3 and as a consequence the axial distance between thevalve seat 28 and the aforementioned abutment surface 38 is reduced.That reduction permits the closure element head portion 27 to engageagainst the valve seat 28 and such engagement preferably occurs shortlyafter operation commences. Continued inward movement of the piston 9results in the aforementioned rod 35 moving further axially into thetubular member 34, and adequate radial and axial clearance is providedfor that purpose.

The tubular member 34 may be held against the cylinder end wall 6 bymeans of the aforementioned biasing spring 13, and in that event mayhave a laterally projecting flange 39 at its terminal end to provide asurface against which the spring 13 can engage. Any suitable means maybe provided to permit fluid to pass between the interior of the tubularmember 34 and the portion of the pressure chamber 14 surrounding thatmember. In the embodiment shown, one or more longitudinally extendingslots 40 are formed through the side wall of the tubular member 34.

Guide means 41 is preferably provided within the piston stem bore 15 toensure that the head portion 27 of the closure element 26 is correctlyaligned with the valve seat 28. That guide means 41 may include a sleeve42 neatly positioned within the end of the stem bore 15 adjacent thereservoir 19 and which slidably contains the aforementioned head portion27. The guide sleeve 42 may also function as a stop which limits thedegree of movement of the head portion 27 away from the valve seat 28.Opposed surfaces of the sleeve 42 and head portion 27 may engage whenthe head portion 27 and valve seat 28 are separated to an extentsufficient to permit adequate fluid transfer between the reservoir 19and the pressure chamber 14.

A coil compression spring 43 acts between the guide sleeve 42 and thetubular member 34 so as to resiliently hold the sleeve 42 against theaforementioned transverse wall 21. That spring 43 allows the sleeve 42to move away from the transverse wall 21 in the event that axialexpansion of the actuator 1 exceeds that at which the aforementionedstop 12 becomes operative.

The head portion 27 of the closure element 26 may be urged against thevalve seat 28 by pressure of the fluid within the pressure chamber 14.For that purpose it is preferred to provide adequate clearance betweenthe closure member rod 35 and the guide sleeve 42 to permit fluid withinthe stem bore 42 to impinge against the head portion 27. Preferably, andas shown, a suitable spring 44 acts between the guide sleeve 42 and thehead portion 27 to augment that valve closing influence.

It is preferred that the aforementioned outlet port 17 is located inportion of the stem side wall 18 which surrounds the guide sleeve 42.Appropriate access passage means 45 may be provided in that sleeve 42 orside wall 18 to ensure proper communication between the outlet port 17and the pressure chamber 14. It is also preferred that the end portion46 of the tubular member 34 adjacent the valve seat 28 is of reduceddiameter to provide a shoulder 47 against which the spring 43 acting onthe guide sleeve 42 can engage. One or more openings 48 may be providedthrough the side wall of that end portion 46 to ensure propercommunication between the stem bore 15 and the interior of the tubularmember 34.

An actuator 1 as described has important advantages over prioractuators. It is of particularly simple and compact construction, andfactors which contribute to that result are the hollow piston stem 10and the connection of the reservoir 19 to that stem 10 rather thandirectly to the cylinder body 3. Another advantage arises from theparticular valve means described. That valve means provides for only onepossible leakage path between the reservoir 19 and the pressure chamber14, whereas two or more such paths generally exist in priorarrangements.

The actuator 1 of the invention is adapted to be included in a simpleand effective actuator assembly. The assembly depicted in FIGS. 3 and 4of the drawings includes a foot pedal 50 which is arranged to causeoperation of the actuator 1.

As shown, the actuator 1 and the foot pedal 50 are each connected to acommon mounting bracket 51 which is adapted to be secured to a vehiclefire wall 52, for example. The bracket 51 in one form has a base 53 anda pair of side walls 54 upstanding from that base. The foot pedal 50 andthe actuator 1 are located between those side walls 54 and each isindependently pivotally connected to the bracket 51 for movement towardsand away from the bracket base 53. The foot pedal 50 and actuator 1 arealso pivotally connected to one another and the arrangement is such thatpivotal movement of the foot pedal 50 causes reduction in the axiallength of the actuator 1 and thereby operates the actuator 1. Thedepressed position of the foot pedal 50 is depicted in FIG. 3 by dottedlines 55.

The pedal 50 has one end 56 pivotally connected to the bracket 51 andhas a foot engaging pad 57 at its opposite end 58. The body 3 of theactuator 1 is pivotally connected to the foot pedal 50 through theaforementioned mounting flange 7, and that connection is at a locationbetween the ends 56 and 58 of the pedal 60. Preferably, the pedal 50 isof channel-shape between its ends and the actuator body 3 is at leastpartially located within that channel under all circumstances of use.The axis 59 of the pivotal connection between the actuator and pedal issubstantially parallel to the axis 60 of the pivot about which the pedal50 moves.

A mounting flange 61 is provided at the end of the piston stem 10 remotefrom the actuator body 3 and that flange 61 is used to pivotally connectthe stem 10 to the mounting bracket 51. Once again the pivot axis 62 issubstantially parallel to the pivot axis 60 of the pedal. In order toachieve the desired operation of the actuator 1, it is generallypreferred to locate the stem pivot 63 adjacent the pedal pivot 64, butat a location closer to the bracket base 53. The arrangement is suchthat inward swinging movement of the pedal to the position shown bylines 55 causes the actuator piston 9 to move further into the cylinderbody 3 thereby pressurising the fluid in the pressure chamber 14.

It will be appreciated that the pedal 50 and actuator 1 need not beconnected to a bracket 51 as described. Furthermore, each may beindependently connected to a support structure rather than through acommon bracket.

An assembly as described is extremely compact and has the advantage ofplacing the actuator 1 under compression when in use. There is thefurther advantage of having the reservoir 19 located in directassociation with the actuator 1 rather than being remote therefrom.

Finally, it is to be understood that various alterations, modificationsand/or additions may be introduced into the constructions andarrangements of parts previously described without departing from thespirit or ambit of the appended claims which define the invention.

I claim:
 1. An actuator for a fluid pressure system including a footpedal pivotally connected to a support structure for movement away fromand into a rest position, a piston-cylinder assembly pivotally connectedat its opposite ends, one end pivotally connected to said foot pedal andthe other end pivotally connected to said support structure saidassembly having a piston slidably mounted within a bore of a cylindermember and a pressure chamber formed at least in part within saidcylinder member, movement of said piston in one direction relative tosaid cylinder member being operable to cause a reduction in thevolumetric size of said chamber, and the two said pivotable connectionswith the support structure being spaced apart so that movement of saidpedal away from said rest position causes movement of said piston insaid one direction and causes movement of said cylinder member relativeto said support structure.
 2. An actuator for a fluid pressure systemaccording to claim 1 wherein said assembly includes a fluid inlet and afluid outlet, said outlet is connectable to means to be operated by saidactuator, a fluid reservoir is connected to said inlet, and valve meansis operable to control passage of fluid through said inlet.
 3. Anactuator for a fluid pressure system according to claim 1 wherein saidpiston-cylinder assembly comprises:a body having a cylindrical boretherein, a piston having a head portion slidably mounted in said boreand a stem which projects out of said body through one end thereof, apressure chamber having a first part formed within said body betweensaid head portion and an end wall of said body at the end thereof remotefrom said one end, a passage within said piston forming another part ofsaid pressure chamber and being in communication with said first part ofthe pressure chamber, a fluid reservoir, orifice means connecting theinterior of said fluid reservoir with said passage, valve means operableto close said orifice means in response to movement of said pistontowards said end wall, and a fluid outlet connected to said chamber. 4.An actuator according to claim 3 wherein said valve means is biased to aclosed position.
 5. An actuator according to claim 3 wherein said valvemeans comprises a valve closure member linked to said body through atie, said tie causing said valve closure member to lift off said orificewhen the piston moves to a rest position remote from the end wall of thebody.
 6. An actuator according to claim 5 wherein said piston is biasedby means of a spring to said rest position.
 7. An actuator according toclaim 6 wherein said spring comprises a compression spring which actsbetween said piston and said end wall and said body is provided with astop formation for limiting movement of the piston out of the bore. 8.An actuator according to claim 3 wherein the reservoir and piston stemare separated by a transverse wall having said orifice therethrough,said orifice defining a valve seat.
 9. An actuator according to claim 3wherein said valve means comprises a valve closure member having a partspherical head covered with a cap of elastomeric material.
 10. Anactuator according to claim 9 wherein the head is connected to a rod andsaid rod extends towards the cylinder and is coupled with a retainingmeans fixed to the body, the connection between rod and retaining meansenabling relative movement between rod and retaining means when thepiston is caused to move into the cylinder, but will lift the head offthe orifice as the piston moves into a rest position remote from the endwall of the cylinder.
 11. An actuator according to claim 10 wherein theretaining means is held to the end wall of the body by a compressionspring which acts between said end wall and the piston to bias thepiston to the rest position.
 12. An actuator according to claim 3wherein the valve means is located within the passage in the piston stemand a guide means is provided in said passage to guide the valve meanstowards the orifice.
 13. An actuator according to claim 12 wherein theguide means is adapted to limit the degree of movement of the valvemeans away from the orifice.
 14. An actuator according to claim 13wherein the guide means is movable within the passage and is biased bymeans of a spring towards the orifice end of the passage.
 15. Anactuator according to claim 3 wherein the fluid outlet is located in thestem of the piston at the end of said piston which is adjacent saidorifice.
 16. An actuator according to claim 3 wherein seal means areprovided between the piston and the bore, said seal means comprising anelastomeric ring seal located in an annular groove formed around thepiston.
 17. An acutator according to to claim 3 wherein the piston andthe body are both formed of a plastic material.
 18. An actuator for afluid pressure system including a foot pedal having a foot pad end and apivoted end, said pivoted end being pivotally connected to a supportstructure for movement between a rearward active position and a forwardrest position, a piston-cylinder assembly having a pivot mounting oneach end and pivotally connected at a first end to a support structureand at a second end to said foot pedal, said pivotal connection of thefirst end of the piston-cylinder assembly to its support structure beingadjacent to but rearward of the pivotal connection of the foot pedal toits support structure, said pivotal connection of said second end of thepiston-cylinder assembly to the foot pedal being spaced away from thepivoted end of the foot pedal and toward the foot pad end thereof, saidpiston-cylinder assembly having a piston slidably mounted within a boreof a cylinder member and a pressure chamber formed at least in partwithin said member, movement of said foot pedal from said forward restposition toward said active position being operable to cause a reductionin the volumetric size of said chamber, and also being operable to causemovement of said piston-cylinder assembly in relation to its supportstructure.
 19. An actuator for a fluid pressure system including agenerally vertically extending foot pedal having an upper end pivotallyconnected to a support structure for movement away from and into a restposition, a generally vertically extending piston-cylinder assemblypivotally connected at its upper end to a support structure andpivotally connected at its lower end to said foot pedal, saidpiston-cylinder assembly having a piston slidably mounted within a boreof a cylinder member and a pressure chamber formed at least in partwithin said cylinder member, movement of said piston in one directionrelative to said cylinder member being operable to cause a reduction inthe volumetric size of said chamber, the two said pivotable connectionsto their support structure being spaced apart, the arrangement beingsuch that movement of said pedal away from said rest position causesmovement of said piston in said one direction and also causes movementof said cylinder member in relation to its support structure.